Electrical relay



May 30, 1939. L. DEVOL ELECTRICAL RELAY Filed NOV. 2'7, 1957 J] fi a 9 *2] 7 *10 v 2 S S H 1. Fig. 2. J? '59 J8 3] E 52 28 Input 54- 35 I: 42 Permanent $25 magnet 26 28 29 41 50 D I P1 5. Fig. 4.

5 IN TOR lee Z l i 56a Jb His ATTORNEY Patented May 30, 1939 UNITED STATES PATENT OFFICE ELECTRICAL RELAY pany, Swissvale, Pa.,

sylvania a corporation of Penn- Application November 27, 1937, Serial No. 176,835

14 Claims.

My invention relates to electrical relays, and particularly to relays of a type known as vibration relays.

In vibration relays, it is customary to support at least one of each pair of contacts on a spring,

and this spring together with the contact constitutes a mechanical system having a natural frequency of its own. In the absence of any provision for preventing it, when the cooperating contact members meet, the impact will cause the spring to vibrate at its natural period, which will cause the contact to open and close rapidly until such time as a sufiicient portion of the energy transmitted to it from the vibrating element has 15 been dissipated. The usual method for preventing this bouncing, as it is generally termed, is to provide a mechanical resistance to motion of the spring. This mechanical resistance will prevent the bouncing but it has certain undesirable features. In the first place, it causes the loss of a certain amount of power, decreasing the sensitivity of the relay and also decreasing its sharpness of tuning. In the second place, it is difiicult to maintain the proper amount of frictional loss due to the fact that the coeflicient of friction between the two contact surfaces may change due to foreign material deposited on the contact surfaces, or chemical changes caused by the atmosphere. This difiiculty is, of course, greatly accentuated by the fact that the frictional resistance must be quite small making the adjustment extremely delicate. One object of my present invention is to eliminate these difliculties by substituting a magnetic attraction for the frictional resistance.

Other objects and characteristic features of my invention will appear as the description proceeds.

I shall describe several forms of relays embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a view partly diagrammatic showing one form of relay embodying my invention. Fig. 2 is a view showing a modification of the relay illustrated in Fig. 1. Fig. 3 is a view similar to Fig. 1 showing another form of relay embodying my invention. Fig. 4 is a detail view showing a portion of the relay illustrated in Fig. 3.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the relay in the form here shown comprises a vibrating reed I of magnetizable material clamped at its lower ends between a pair of magnetizable blocks 2 which connect the like poles, as here shown the south poles of a pair of permanent magnets 3, and having its upper end disposed between pole pieces 4 formed on a magnetizable yoke 5 which connects the north poles of the permanent magnets 3. The yoke 5 is provided with an energizing winding 6, and the parts are so proportioned that when the winding 6 is supplied with current of the proper frequency the reed I will vibrate at its natural period.

Secured to the upper end of the reed I are two contact buttons I and 8 which cooperate respectively with contact buttons 9 and III attached to flexible contact fingers I I and I2 to form contacts |9 and 8-"). The fingers II and I2 are secured to the pole pieces 4, but are insulated from the pole pieces by means of insulating blocks I3.

With the relay constructed in the manner thus far described, it will be apparent that when the reed I is vibrating the contact buttons I and 8 will alternately engage the contact buttons 9 and I0, and will thus cause the contacts I9 and 8I0 formed by these contact buttons to become alternately opened and closed. It will also be apparent that since the reed I will be moving at a relatively high rate of speed when the contact buttons I and 8 move into engagement with the contact buttons 9 and I0, the resulting impact will tend to cause the contact fingers II and I2 to vibrate at their natural period, which will of necessity be relatively high, and the vibration of these fingers will tend to rapidly make and break the associated contact a number of times when the contact should be closed. This contact bounce" as it is generally termed tends to cause arcing at the contact buttons, and if the fingers are permitted to vibrate, any circuits which are controlled by the contacts will be opened many times while they should be closed, thus causing a loss in the amount of thepower output of the relay. Furthermore, this arcing tends to burn the contact buttons, causing the contact buttons to fail by pitting or entire loss of contact. Any amount of burning is undesirable since it changes the contact adjustments and contact pressure.

In accordance with nry present invention, the tendency of the contact fingers to vibrate relative to the reed when the contact button carried by the reed moves into engagement with the contact button secured to the finger is prevented by making the fingers of magnetizable material, and by so shaping the upper end of the reed that when the reed moves to the position in which either contact becomes closed, the reed will be separated from the adjacent finger by a relatively small air gap. With this construction, when the reed swings to the left, for example, thus causing the contact 19 to become closed, flux from the lefthand permanent magnet 3 will pass to the lefthand pole piece 4, the air gap between the pole piece 4 and the contact finger II, the air gap between the finger II and the T-shaped upper end of the reed, the reed, and the left-hand block 2 back to the left-hand magnet 3, which fiux will create an attractive force between finger II and reed I. This force will hold the contact buttons 1 and 9 firmly together until, during the return swing of the reed, the finger I I moves into engagement with a non-magnetic stop I4 which is provided between the upper end of the fingers I I and I2 to limit the amount of movement of the fingers, whereupon the motion of the finger II will be arrested and the contact will become opened. The operation of the relay when the reed swings toward the right is similar to that just described when the reed swings toward the left, and will be apparent from the foregoing description without further detailed description. The fingers II and I2 need be made only sufiiciently stiff to insure that when the reed is in equilibrium position the contacts will not become closed due to the magnetic attraction which then exists between the fingers and the reed. The amount of the fiux which passes through the fingers II and I2 may be limited by the dimensions of the fingers, and by the air gaps which are provided between the fingers and the pole pieces 4 by the insulating blocks I3, so that the force holding the fingers against the reed may be made to have any desired value.

Referring now to Fig. 2, in the modified form of the relay here shown the reed of the relay, which reed is here designated by the reference character I5, is provided at its upper end with a nonmagnetic separator I8, a magnetizable block I1, a non-magnetic spacer I8, and a permanent magnet I9 having a T-shaped upper end. Furthermore, as here shown, the contact buttons 1 and 8, instead of being secured to the reed, are secured to the opposite sidesof the permanent magnet I9, and the contact buttons 9 and II) with which the contact buttons 1 and 8 cooperate, instead of being attached to the fingers II and I2, are attached to resilient magnetizable fingers 20 and 2I which depend from fixed supports 22 and 23, respectively. The movement of the fingers 20 and 2I toward each other is limited by a stop 24 which is mounted between fingers 29 and 2I directly above the T-shaped upper end of the magnet I9.

The operation of the relay shown in Fig. 2 is as follows: When winding 6 is supplied with alternating current of the proper frequency, the reed I5 will vibrate at its natural period, and will thereby alternately open and close the contacts 19 and 8-! in substantially the same manner that the vibration of the reed I of the relay shown in Fig. 1 alternately opens and closes the contacts 19 and 8-) of this relay. When the reed swings to the position in which the contact 1-9 becomes closed, flux will pass from the lower end of magnet I9 through the gap formed by spacer I8, magnetizable block I1, the air gap between block I1 and finger 20, finger 28, and the air gap between finger 29 and the head of the magnet, back to the magnet, and will thus create a force between the finger 20 and the magnet which tends to prevent the contact button 9 from bouncing. The parts are so proportioned that on the return stroke of the reed the button 9 will remain in contact with the button 1 until after button 8 moves into engagement with button III, and as a result a portion of the flux from magnet I9 will pass through finger 2I while fiux is still passing through the finger 28. When the flux is passing through both fingers, the fiux through finger 29 will be reduced to approximately one-half of its previous value, and it follows therefore that when the reed finally moves away from finger 29 it will do so with a retarding force approximately onefourth as great as would be present if a portion of the fiux from the magnet were not passing through the finger 2|. Thus, the force tending to hold the contact closed may be made nearly four times as great without anyincrease in the retarding impulse given to the reed when it pulls away from the spring. This makes possible a firmer contact without any appreciable interference with the normal frequency characteristic of the reed. The action of the relay when the reed swings toward the right is similar to that when it swings toward the left, and will be apparent from the foregoing description without further detailed description.

Referring now to Figs. 3 and 4, the relay here shown comprises a permanent magnet 25 providing a polarized field for a vibrating reed 28 which carries an energizing winding 21, whereby, when current of the proper frequency is supplied to the winding 21, the reed 26 will vibrate at its natural period. The free end of the reed 26 carries a magnetizable block 28 which is spaced from the reed by a non-magnetic separator 29, and secured to the opposite sides of the block 28 are two contact buttons 30 and 3| of non-magnetizable material which cooperate with two contact buttons 32 and 33 attached to flexible contact fingers 34 and 35, respectively. The fingers 34 and 35 are of magnetizable material and are secured at their lower ends to magnetizable blocks 36a and 361) which are disposed on opposite sides of the lower end of a permanent magnet 42. The upper ends of the fingers 34 and 35 cooperate with stops 31 and 38 and are provided with projections 39 and 40. The parts are so proportioned that the stops 31 and 38 will prevent the fingers from moving toward each other beyond positions very near to their equilibrium positions, and that when either finger is moving toward the other finger the projections 39 and 40 will engage each other before the moving finger strikes the associated stop. Fingers 34 and 35 are of equal mass, and projections 39 and 40 are of non-magnetic material. Also secured to the block 28 are two magnetizable projections H and Ma which protrude toward springs 34 and 35, and the function of which will appear presently. The upper end of the permanent magnet 42 is disposed directly below the block 28, and is provided with a magnetizable block 43, preferably of soft iron.

The operation of the relay shown in Fig. 3 as a whole is as follows: When reed 26 swings toward the left, it brings projection 4I close to finger 34, and magnetic fiux passes from magnet 42 through block 28, projection 4I, finger 34, and block 36a back to magnet 42. This fiux exerts a force on the finger 34 which tends to hold the contact formed by the buttons 38 and 32 closed, and thus prevents bouncing of the contact. When the reed 26 starts to swing in the opposite direction, projection 39 will strike projection 40 before finger 34 strikes stop 31, and will transmit to finger 35 almost all of the momentum of spring 34, and the parts mounted on it, thereby giving to finger 35 a velocity about as great as the velocity of finger 34 at the time of the impact, and hence almost as great as the velocity of reed 26.

As reed 26 and finger II continue their motion toward the right, reed 2. almost immediately catches up with finger II, thereby closing contact Sl-Ii, and since the velocity of reed 2i and finger 85 are almost identical at the time that the contact is made the impact is very slight. The motion of the reed toward the right also moves projection ll away from finger 34 and projection lla close to finger 35, thereby materially decreasing the magnetic pull exerted on finger 34 by the magnet 42 and causing a magnetic pull to be exerted on finger 35, in a manner which will be readily imderstood from an inspection of the drawing. It will be obvious, of course, that as soon as finger It strikes stop 31, the continuing motion oi the reed 26 toward the right will break the contact -32 if it has not already become broken when the projection It strikes the projection ll. When the reed starts to again swing toward the left, the momentum of finger 35 will be transmitted to finger 34 through the projection ll striking the projection 39, and the parts will then function in a manner similar to that when the reed swings toward the right.

One advantage of the structure shown in Figs. 3and4isthatthisstructure,inadditionto efiectively preventing contact bounce, makes possible the use of weaker fingers for supporting the contact, thereby reducing the amount of energy dissipated in the contact and the associated finger to a minimum, thus permitting the relay to be operated on a minimum amount of power.

Although I have herein shown and described only three forms of electrical relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope oi my invention.

Having thus described my invention, what I claim is:

1. A relay comprising a magnetizable vibratory reed, means including a polarizing magnet for vibrating said reed, a magnetizable flexible con tact finger forming a path for fiux from said magnet to said reed whereby when said reed swings toward said finger a magnetic attraction will exist between said reed and said finger, and cooperating contact members secured to said reed and said finger respectively and adapted to be moved into engagement by the motion of said reed toward said finger.

2. A relay comprising a vibrating reed, means including a permanent magnet for supplying a polarizing field to said reed and an electromagnet for causing said reed to vibrate, a flexible magnetizable contact finger mounted in such a position that said reed will alternately swing toward and away from said finger and that when said reed swings toward said finger fiux from said polarizing magnet will pass through said reed and said finger to create a magnetic attraction between them, and cooperating contact members mounted on said reed and said finger.

3. A relay comprising a vibrating reed, means including a permanent magnet for supplying a polarizing field to said reed and an electromagnet for causing said reed to vibrate, a flexible magnetizable contact finger mounted in such a position that said reed will alternately swing toward and away from said finger and that when said reed swings toward said finger fiux from said polarizing magnet will pass through said reed and said finger to create a magnetic attraction between them, cooperating contact members mounted on said reed and said finger, and a stop for limiting movement of said finger toward said reed.

4. In combination with a magnetizable vibratory element and means for driving said element including a permanent magnet for supplying a polarizing field to said element, a flexible magnetizable contact finger carrying a contact member adapted to cooperate with a contact member carried by said vibratory element, said finger being so disposed with relation to said element and said magnet that fiux from said magnet will create a magnetic attraction between said element and said finger when said contact members are in engagement to prevent contact bounce.

5. In combination with a magnetizable vibratory element and means for vibrating said element, a permanent magnet secured to said element, a flexible magnetizable contact finger carrying a contact member adapted to cooperate with a contact member carried by said element, said finger being so disposed with relation to said magnet that when said contact members are in engagement said finger will be attracted to said magnet, whereby contact bounce is prevented.

6. In combination, two permanent magnets having their like poles connected together at one end by a magnetizable yoke provided with confronting spaced pole pieces and with an energizing winding, two magnetizable blocks disposed between the other ends of said magnets, a vibratory magnetizable reed clamped at one end between said blocks and having its other end disposed between the poles of said yoke, whereby when said winding is supplied with current of the proper frequency said reed will vibrate, two fiexible contact fingers secured to but insulated from the pole pieces of said yoke on opposite sides of said reed in the direction of its movement, and cooperating contact members secured to said reed and said fingers, said reed being so shaped that when either contact formed by said members is closed said reed will be spaced from the contiguous finger by a small air gap.

7. In combination, two permanent magnets having their like poles connected together at one end by a magnetizable yoke provided with confronting spaced pole pieces and with an energizing winding, two magnetizable blocks disposed between the other ends of said magnets, a vibratory magnetizable reed clamped at one end between said blocks and having its other end disposed between the poles of said yoke, whereby when said winding is supplied with current of the proper frequency said reed will vibrate, two flexible contact fingers secured to but insulated from the pole pieces of said yoke on opposite sides of said reed in the direction of its movement, cooperating contact members secured to said reed and said fingers, said reed being so shaped that when either contact formed by said members is closed said reed will be spaced from the contiguous finger by a small air gap, and a stop member disposed between said fingers for limiting their movement toward said reed.

8. In combination with a vibratory element and means for vibrating said element, a magnetizable block secured to the free end of said element but spaced therefrom by a non-magnetic separator, a permanent magnet movable with said element and spaced from said magnetizable tool: in such nt swings permanent ma g and bloc}; Y c attraction between finger let, a stop for limiting the rnovem sponse the pull GXGl'tE-J. by said and coo contact members sesaid et and said finger. In. combination, vibratory element, means ating said element, a magnetizable blocl; ed to said element, a flexible magnetizable 1 tact finger, ccperating contact members carby said finger and said element respectively, and a permanent magnet having one end disposed adjacent said bloclr and the other end ma neticaily connected with said contact finger in such manner that when said contact members are in engagement a magnetic attraction will exist between said finger and said block, whereby contact bounce is prevented.

10. In combination, a vibratory element, means for vibrating said element, flexible contact fingers disposed on opposite sides of said element in the direction of its movement, cooperating contact members carried by said element and said fingers, resilient projections on the free ends of said fingers so arranged that when said element is swinging toward either finger said projections will engage before the contact member on such finger is engaged by the cooperating contact member on said element and before the other contact member on said element moves out of engagement with the contact member on the other finger, whereby an initial velocity approaching the velocity of the vibrating element is imparted to either finger before the contact member carried by such finger is engaged by the coperating contact member carried by the reed, to decrease contact bounce.

11. In combination, a vibratory element, means for vibrating said element, flexible contact fingers disposed on opposite sides of said element in the direction of its movement, cooperating contact members carried-by said element and said fingers, resilient projections on the free ends of said fingers so arranged that when said element is swinging toward either finger said projections will engage before the contact member on such finger is engaged by the coperating contact member on said element and before the other contact member on said element moves out of engagement with the contact member on the other finger, whereby an initial velocity ap proaching the velocity of the vibrating element is imparted to either finger before the contact member carried by such finger is engaged by the combi tion, a viina'tory cler' "id ele fingers, resilient projections on the said fingers so arranged that W17. is swinging toward either said prc ec will engage before the contact member on such finger is engaged by the cooperating contact r rem-- her on said element and before the other contact member on said element moves out of engagement with the contact member on the other finger, whereby an initial velocity approaching the velocity of the vibrating element is imparted to either finger before the contact member carried by such finger is engaged by the cooperat ing contact member carried by the reed to decrease contact bounce, means for creating a magnetic attraction between said element and either finger toward which said element is swung, and stops for limiting the movement of each finger toward the other finger to a relatively small distance beyond its equilibrium position.

13. A relay comprising a magnetizable vibrating reed, means including a magnet for vibrating said reed, a flexible magnetizable contact fin ger, cooperating contact members carried by said reed and said finger, means to create a magnetic attraction between said reed and said finger when said reed swings to bring said contact members into engagement-to prevent contact bounce, and stop means to limit the movement of the finger with the reed when the reed swings to break engagement between said contact members.

14. A relay comprising a magnetizable vibrating reed, means including a magnet for vibrating said reed, two flexible magnetizable contact fingers one disposed on each side of the reed in its direction of motion, coperating contact members carried by said reed and said fingers and forming contacts which are alternately opened and closed by the movement of said reed when the reed is vibrating, means for exerting magnetic attraction between either finger and the reed when the contact member secured thereto is engaging the cooperating contact member on said reed to prevent contact bounce, and stop means to arrest the movement of either finger to disengage the contact member secured thereto from the cooperating contact member on said reed when the reed swings away from that finger.

LEE DEVOL. 

